On Wed, 2007-05-23 at 11:24 +0200, Terje J. Hanssen wrote: > Herman Robak wrote on Tue, 22 May 2007
> > The display has to be stretched by the player. If Cinelerra is told > > that the resolution is 1440x1080 and the aspect ratio is 16:9, it will > > scale the image to fit the specified aspect ratio. > > Yes, but is this managed by filling out with more pixels horisontally on > the display? > If I'm right the display pixels are square i.e on a UWXGA LCD 1920x1200 in > aspect ratio 16:10=1.6 > I can't see how else the video frame can get the right 16:9 aspect ratio > geometry... That is correct. The player (here: Cinelerra) has to interpolate the 1440 "source" pixels into 1920 "screen" pixels. And the player assumes square screen pixels, which _may_ be wrong, even for computer displays. The important term here is "pixel aspect": the aspect ratio of the pixels. 1440:1080 = 12:9. 1920:1080 = 16:9. So 12 source pixels need to be stretched to 16 screen pixels. That gives you a pixel ratio of 16:12, or 4:3. That's a fairly nice pair of numbers, compared to the oddball pixel ratios of NTSC and PAL. 720p HDV has square pixels, i.e. 1:1 pixel aspect. 1280:720 = 1:1. And no pesky interlacing, as the 'p' suggests. > > Everything in your project will have to take those non-square pixels > > into account, as the "native" shape of the 1080i HDV pixels is > > rectangular. The same goes for 4:3 DV, to a modest extent. > > > > But SD DV25 PAL uses "almost square" pixels and its rectangular aspect > frame 4:3=1.33 almost just come from more horisontal than vertical pixels > 720:576=1.25 if I'm right here ... (?) You're right. "Screen PAL" would be 768x576, which is 4:3. The difference is noticable, though quite subtle. > > I don't think you'll find HDMI inputs. Just like there are no > > cheap and common VGA or DVI "grabbers". Those interfaces are one > > way only. > > HDMI input is available on Black Magic Design's "Intensito Pro" HDMI > capture and playback card, but sorry, on several requests and interest > from Linux users, they have not been willingly to support Linux so far. Maybe you should check out SDI instead. There is little point in grabbing HDMI output from recorded tape. By the time you have recorded to tape, the video is already compressed, lossily, and the tape becomes the "original". The decoding in the camera is actually a slight generation loss; a pointless loss, unless your software decoders are truly sucky! Are you considering hard disk recording of uncompressed HD video? That will require a striping RAID, so it will be heavy and pricey. You might as well get a semi-pro camera with SDI-HD output, which is intended for such use. Or are you in the "I did it because I could" camp? ;-) -- Herman Robak _______________________________________________ Cinelerra mailing list [email protected] https://init.linpro.no/mailman/skolelinux.no/listinfo/cinelerra
